Selectorized dumbbells are known which allow the user to easily adjust the amount of the exercise mass coupled to the handle. This is done by the manipulation or repositioning of a selector to change the number of weights that are coupled to the handle from among a plurality of nested weights that are available to be so coupled. This avoids having to purchase and store an entire set of dumbbells in different weights, e.g. a pair of 5 lb. dumbbells, a pair of 10 dumbbells, etc. This also avoids having to individually slide more weight plates onto or off of each end of a bar type dumbbell handle in order to increase or decrease, respectively, the exercise mass of the dumbbell.
One type of selectorized dumbbell is shown in U.S. Pat. No. 5,637,064 issued to the Applicants hereof. In this selectorized dumbbell, one weight plate is joined to a second laterally spaced weight plate by a front rail connected at either end to the front sides of the weight plates and by a rear rail connected at either end to the rear sides of the weight plates. The front and rear rails joining the pair of weight plates are at the same vertical elevation relative to one another. Thus, a single weight used in the selectorized dumbbell is formed by the pair of weight plates and by the pair of rails used to join the weight plates together.
In this selectorized dumbbell, a plurality of weights of the type described above are used which weights are generally identical to one another except in two respects. First, the lateral spacing between the weight plates from one weight to another progressively increases as one goes from an innermost weight to an outermost weight, thus causing the front rails to progressively increase in length in a like manner. Second, as one goes from an innermost weight to an outermost weight, the rails lower in height with the rails on the innermost weight being the highest, the rails on the outermost weight being the lowest, and the rails on the weights in between being at progressively different heights between the highest and lowest heights. This allows the weights to be nested together with the weight plates on a first end of the rails, namely the left weight plates, being stacked together and spaced from the stacked weight plates on the second end of the rails, namely the right weight plates, such that a gap is provided between the stacks of left and right weight plates. In this design, the front and rear rails are stacked on top of another along the front and rear sides of the weight plates in front and rear vertical rail arrays.
The handle of the dumbbell has a pair of spaced ends that carry a vertical array of slots therein. The slots are located in alignment with vertical spaces between the adjacent rails when the handle is dropped down and inserted into the gap between the stacks of left and right weight plates. The handle carries a hand grip that is perpendicular to the handle ends and perpendicular to the direction of the slots.
A U-shaped connecting pin is inserted beneath the front rails of a selected weight with the prongs of the U-shape entering into a pair of slots in the opposite ends of the handle. The prongs will extend through fully through such slots as the user fully pushes the connecting pin into the handle. The amount of exercise mass coupled to the handle is determined by which of the spaces beneath the rails receives the connecting pin. When coupled in this manner, the handle will lift an exercise mass comprising both the weight whose rails are immediately above the connecting pin and any other weights that are above the selected weight. The exercise mass can thus be easily adjusted by moving the connecting pin upwardly or downwardly to the spaces beneath the rails of different weights before pushing the connecting pin inwardly.
While a selectorized dumbbell of this type is very effective and easy to use, the front and rear rails must be robust enough to carry the spaced weight plates in a durable manner. Typically, the rails comprise steel bar stock of at least a ¼″ in diameter. In addition, each end of the rail must be welded to either the front or rear side of each weight plate. Thus, there are four welds required when manufacturing each weight. Thus, this style of weight can be somewhat costly to manufacture.
In addition, the insertion of the connecting pin into the handle beneath the lowermost rails, i.e. the rails of the outermost weight in which the laterally spaced weight plates are the furthest apart, can be somewhat difficult given the small clearance between the space beneath such rails and a support surface on which the nested weights of the dumbbell are resting. The user must take care to ensure that the connecting pin is almost perfectly horizontal before attempting to push it into the slots in the handle that are aligned with the space beneath the rails on the outermost weight. In addition, the center of gravity of the dumbbell lowers as more weights are added to the handle due to the added mass of the front and rear rails of the added weights. This change in the center of gravity can be felt by the user and is undesirable.
It would be better if the weight distribution of the dumbbell felt the same in the user's hand regardless of how many weights were coupled to the handle. Thus, it would be a further advance in the art to provide a selectorized dumbbell that had an improved, more easily usable selector and that had a consistent center of gravity regardless of the numbers of weights coupled to the handle.